When a home electronic device is remotely controlled by a wireless communication system using a 2.4 GHz ISM (Industrial, Scientific and Medical use) band, the influence of obstructions becomes smaller and the coverage range becomes larger than by an infrared communication system. In addition to such a wireless communication system, this band has been also assigned to microwave heating. Thus, there is a problem that unnecessary radio waves (hereinafter referred to as interference waves) radiated from a microwave oven that performs microwave heating adversely interfere with the home wireless communication system. In the microwave oven, a magnetron generates microwaves of a 2.4 GHz to 2.5 GHz frequency band. In addition, there are two magnetron driving types, a transformer type and an inverter type.
In the transformer type, a commercial power supply voltage of, for example, 50 Hz is raised by a transformer and the raised voltage is applied to the magnetron. Thus, in one period T (20 ms) of a sine wave shown in FIG. 1A of the commercial power supply voltage, a non-operative region of a negative half period T1 (10 ms) occurs as shown in FIG. 1B. For example, in a real microwave oven product, the oscillation frequency of the magnetron is 2.45 GHz and electromagnetic waves periodically occur five times in an operative region (positive half period). In the inverter type, after a power supply voltage is full-wave rectified, the rectified voltage is switched by a switching device, the resultant voltage is raised by a transformer, and then applied to the magnetron. Thus, in the inverter type, until the commercial power supply voltage has been raised up to an operation start voltage of the magnetron, microwaves do not occur and a non-operative region T2 (1 to 2 ms) occurs as shown in FIG. 1C. In these non-operative regions T1 and T2, since microwaves do not occur, no interference with wireless communication occurs.
A technique of compressing information data and transmitting the compressed information data in the foregoing non-operative region T1 or T2 taking into account of the fact that a microwave oven generates interference waves in synchronization with the period of a commercial power supply is described in patent document, “Japanese Patent Application Laid-Open No. HEI 11-112441”.
In addition, patent document, “Japanese Patent Application Laid-Open No. 2002-111603” describes a technology of which when a non-operative region has not been detected from a commercial power supply and an interference wave detecting section has detected a good environment in which there is no influence of interference waves, the frequency is hopped to another frequency and that when electromagnetic waves that a microwave oven had generated have been received as interference waves, the frequency of a control signal that serves to secure a communication connection state is changed to another frequency that the interference waves do not influence.
In the foregoing methods of the related art, since a frequency distribution of interference waves is not considered, the influence of interference waves is not sufficiently excluded. When the influence of interference waves to the transmission side is different from that to the reception side, their influences are not sufficiently reduced. For example, in a house, besides a microwave oven, there is another interference source such as a wireless LAN.